When you first placed a building, you were able to move and rotate it as you like in the Editing mode. To return to this mode, tap the building and hold your finger on it for one second.
You will see three buttons atop of your building: store, rotate and apply changes.
To move the building in this mode, tap it and slide to wherever you want it to be. Tap Rotate to change the building's orientation. Tap Apply to save changes.
If you tap the Store button on the left, your building will be placed in the Storage. To open the Storage, tap the middle button in the lower right corner of the screen.
For your convenience buildings in the storage are split into categories. Some categories may be gray, this means that you have no buildings stored in them.
Tap a category to find your building. Finally, tap the building once to place it in your town again.